1. Field of the Invention
The present invention relates to a microbead analysis method and a microbead analyzer. More specifically, the present invention relates to, for example, microbead analysis by using a microbead carrying a pattern formed thereon for image identification of individual bead.
2. Description of the Related Art
Particulate carriers, traditionally called “microbeads”, have been used in biochemical analysis, for example, of nucleic acids and proteins. For example in nucleic acid analysis, a microbead carrying a probe nucleotide chain that has a base sequence complimentary to a target nucleotide chain and is immobilized on the surface is used for isolation of the target nucleotide chain in interaction thereof with the probe nucleotide chain. Alternatively in protein analysis, a target protein is isolated similarly by using a microbead with an antibody to the target protein being immobilized on the surface.
It is possible to detect optically the target nucleotide chain or target protein captured and separated on the microbead surface, if it is previously labeled with a fluorescent substance. In addition, measurement of the fluorescence intensity on the bead surface allows quantitative determination of the separated target substance. When the target substance is a nucleotide chain, the target nucleotide chain separated can be optically detected, if an intercalator that emits fluorescence when incorporated in the hybrid chain formed in interaction between the target nucleotide chain and the probe nucleotide chain is used.
Recently, biochemical analysis using such a microbead demands further improvement in throughput and there are various technologies developed for further increase in the processing speed of analysis.
For example, Japanese Patent No. 3468750 (hereinafter, referred to as Patent Document 1) discloses “a method of detecting multiple analytes in a sample, which are recognized by their analysis reaction products, including: a) bringing various kinds of fluorescence particles each having a different fluorescence signal and a different analysis reaction product, the analysis reaction product binding specific to one analyte in the sample, the fluorescence particles each having at least one nanoparticle labeled with a fluorescent dye on the surface, into contact with a sample; b) adding the sample to a labeling reagent; c) analyzing the fluorescence particles indicating that the analysis reaction product is bound to the analyte by detection of the label; and simultaneously, d) determining the fluorescence particles bound to the respective analytes from the function of the different fluorescence signals associated with the respective fluorescence particles” (see Claim 23).
In the “Suspension Array Technology” provided by Luminex Corporation based on the technology, it is possible to identify up to 100 kinds of microbeads by labeling microbeads with two kinds of fluorescence colorants with some modification in the color of the emitted light. It is possible by the “Suspension Array Technology” to analyze 100 kinds of different target nucleotide chains or target proteins simultaneously in one analysis, by immobilizing different probe nucleotide chains or antibodies on 100 kinds of microbeads.
Patent Document 1 above also describes “The fluorescence particles are defined additionally by the size and the shape thereof” (see Claim 25) and discloses that it is possible to use the size and shape of the microbead as an additional parameter for identification of the microbead (see, for example, paragraph 0037 etc. in Patent Document 1).
Relevantly, a technique of forming a dot code allowing image identification on microbead is disclosed in “Multifunctional encoded particles for high-throughput biomolecule analysis.” (Science, 2007, Vol. 315, No. 5817, p. 1393-6. (hereinafter, referred to as Non-patent Document 1)). It is possible by the technique to prepare a great many kinds, more than 1,000,000 kinds, of microbeads. The document describes that a microbead carrying a dot code formed on half of the elliptical surface of the bead and a probe nucleotide chain immobilized on the other half surface was prepared by photolithography in channel (see FIG. 1 in Non-patent Document 1).